how do i interpret the results

7/28/2019 How Do i Interpret the Results

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ISOFFICE-BASEDSPIROMETRYPOSSIBLE?

HOWDOI INTERPRETTHERESULTS?

42QUESTION

Daniel J. Weiner, MD

Office-based spirometry is indeed possible, but not necessarily easy. The resources

required are a cooperative patient, proper equipment, and experienced staff with ade-

quate time. Most children over the age of 6 can perform spirometry, and there is goodevidence that a substantial portion of 4- to 5-year-old children can as well. Younger or

less cooperative patients may require more time to test. A number of manufacturers make

spirometry equipment that is laptop-based and suitable for office use. Some manufactur-

ers use disposable flow sensors, which may have some potential for erroneous results.1

Others use traditional differential pressure pneumotachs with disposable mouthpieces/

filters. These devices can be obtained for $1500 to $2500.

Probably more important than the equipment, however, is having staff trained in

coaching the patient to properly perform spirometry. Spirometry requires the patient to

take a maximal inhalation followed by a maximal and prolonged exhalation. Submaximal

efforts can give very inaccurate results, underestimating some parameters (vital capac-ity, forced expiratory volume in one second), while potentially overestimating others

(forced expiratory flow between 25% and 75% of vital capacity, FEF25-75). Testing sessions

also require that these difficult maneuvers be performed several times and demonstrate

reproducibility. This can require a great deal of patience on the part of the staff, who must

also be able to work with children of different ages. A healthy, cooperative patient might

be able to perform an acceptable test in approximately 10 to 15 minutes, but a distractible

patient performing the test for the first time might require 30 minutes. If the pediatri-

cian wished to assess responsiveness to a bronchodilator (Figure 42-1), this requires the

ability to administer bronchodilator (2 minutes by metered-dose inhaler, and 10 minutesby nebulizer), wait 15 minutes for bronchodilator effect, and then repeat spirometry (an

additional 10 to 15 minutes). This time requirement may be difficult to accommodate in


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214 Question 42

Additionally, technician coaching is improved with regular experience. If spirometry is

performed infrequently and irregularly, it is difficult to maintain good test quality.

The feasibility of performing office spirometry has been examined in both adultand pediatric populations. In one study, 10 pediatric practices were each provided with

10 hours of didactic and hands-on instruction and were expected to perform at least

30 spirometries over 12 weeks.2 Feedback on the test quality was provided by pediatric

pulmonologists. Thereafter, 109 children underwent spirometry both in the office setting

and the hospital PFT laboratory. The good news is that 78% of the office tests were con-

sidered acceptable by American Thoracic Society criteria. The bad news was that 21% of

studies were not interpreted correctly by the pediatricians. One of the conclusions of this

study was that an integrated approach, involving both the primary-care center and the

pulmonologist, is important to ensure quality results. The National Asthma Education

and Prevention Program Expert Panel 3 recommends that when office spirometry showssevere abnormalities, or if questions arise regarding test accuracy or interpretation, fur-

ther assessment should be performed in a specialized pulmonary function laboratory.3

Many spirometry software systems will provide a computerized interpretation of the

results. I have found that these interpretations perform better for tests in adults than in

children and perform poorly if the test quality itself is suboptimal. It is critical that pedi-

atric reference equations be used by the computer when testing children; inappropriate

use of adult equations can provide very misleading results. There are several excellent

resources for learning about spirometry performance and interpretation,4,5 but doing

this well also requires doing it frequently. If you choose to undertake office spirometry,

consider exploring whether your local pediatric pulmonologist is able to assist with inter-

preting study results.

Figure 42-1. Flow volume curvebefore (green) and after (red)bronchodilator, demonstrating sig-nificant bronchodilator response.Pre-bronchodilator FEV

1

74%predicted, FEV1/FVC ratio 58%,FEF25-75 36% of predicted. Post-bronchodilator FEV1 118% pre-dicted (23% increase), FEV1 92%predicted, FEF25-75 49% predicted(36% increase). These results areconsistent with but not diagnosticfor asthma.


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Is Office-Based Spirometry Possible? 215

References

1. Townsend MC, Hankinson JL, Lindesmith LA, Slivka WA, Stiver G, Ayres GT. Is my lung function really thatgood? Flow-type spirometer problems that elevate test results. Chest. 2004;125:1902-1909.

2. Zancanato S, Meneghelli G, Braga R, Zacchello F, Baraldi E. Office spirometry in primary care pediatrics: apilot study. Pediatrics. 2005;116:792-797.

3. National Asthma Education and Prevention Program. Expert panel report 3 (EPR-3): guidelines for the diagnosisand management of asthma. Bethesda, MD: National Heart, Lung, and Blood Institute, 2007. NIH publicationno. 08-4051.

4. Spirometry fundamentals. University of Washington Interactive Medical Training Resources, Seattle, WA.Retrieved from www.depts.washington.edu/imtr/spirotrain/programs/spirofun/index.html.

5. Quanjer P. Become an expert in spirometry. Retrieved from www.spirxpert.com/.


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xviii Contributing Authors

Jennifer LeComte, DO(Questions 17, 18, & 44)

Internal Medicine-Pediatrics

Pediatric Chief Resident

Nemours at the Alfred I. duPont Hospital

for ChildrenWilmington, Delaware

Holger Link, MD (Question 25)

Clinical Associate Professor

Oregon Health & Science University

Department of Pediatrics

Division of Pediatric Pulmonology

Doernbecher Childrens Hospital

Portland, Oregon

Stephen J. McGeady, MD (Questions 15,

19, & 45)

Allergy, Asthma and Immunology

Specialist

Director, Allergy & Immunology

Fellowship program


for Children

Division of Allergy, Asthma& Immunology

Wilmington, Delaware

Sheela Raikar, MD (Question 16)

Pediatric Gastroenterology Fellow

Thomas Jefferson University


for Children

Wilmington, Delaware

Gabriela Ramirez-Garnica, PhD, MPH

(Question 48)

Nemours Childrens Clinic

Orlando, Florida

Amy Renwick, MD (Questions 21 & 27)

Assistant Professor of Pediatrics

Jefferson Medical College

Philadelphia, Pennsylvania

Director of Primary and

Consultative Pediatrics

Julie Ryu, MD (Question 46)

Associate Clinical Professor of Pediatrics

University of California, San Diego

Department of Pediatrics, Division of

Respiratory MedicineRady Childrens Hospital-San Diego

San Diego, California

Jonathan M. Spergel, MD, PhD (Questions 10,

11, & 12)

Associate Professor of Pediatrics

The Childrens Hospital of Philadelphia

Division of Allergy and Immunology

Perelman School of Medicine

University of Pennsylvania


Concettina (Tina) Tolomeo DNP, APRN,

FNP-BC, AE-C (Questions 28, 38, 39, 40,

& 47)

Nurse Practitioner

Director of Program Development

Yale University School of Medicine

Section of Pediatric Respiratory MedicineNew Haven, Connecticut

Daniel J. Weiner, MD (Questions 41 & 42)

Division of Pulmonary Medicine

Co-Director, Antonio J. & Janet Palumbo

Cystic Fibrosis Center

Medical Director, Pulmonary Function

Laboratory

Childrens Hospital of Pittsburgh of UPMC

Pittsburgh, Pennsylvania

Lisa B. Zaoutis, MD (Question 36)

Assistant Professor of Pediatrics

The Perelman School of Medicine at

the University of Pennsylvania

Director, Pediatric Residency Program

The Childrens Hospital of Philadelphia



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